Hydrodroma bruneiensis, Pešić, Vladimir, Chatterjee, Tapas, Marshall, David J. & Pavićević, Ana, 2011

Pešić, Vladimir, Chatterjee, Tapas, Marshall, David J. & Pavićević, Ana, 2011, New records of water mites (Acari: Hydrachnidia) from Brunei Darussalam, Borneo, with descriptions of two new species, Zootaxa 3018, pp. 50-58 : 51-55

Hydrodroma bruneiensis sp. nov.

( Fig. 2–3 ; tables 1–2)

Type series. Holotype, male, dissected and slide mounted, Brunei Darussalam, Gadong, Universiti Brunei Darussalam, freshwater pond (approx 625 m 2) with fringing vegetation (4º58' N, 114º53' E), 20.iii.2011, leg. T. Chatterjee & D. J. Marshall. Paratypes: 7 males, 5 females, same data as holotype, one male and one female dissected and slide mounted in Hoyer's fluid.

Diagnosis. Characters of the genus Hydrodroma ; each genital plate with 56–67 acetabula in 5–6 rows; palpal segments stocky (L/H P-4 4.1–4.4, P-5 3.1–3.5 in both sexes); number of swimming setae on II-Leg-5, 4–5; swimming setae are absent from the anterior surface of IV-Leg-5.

TABLE 1. Morphometric data for the genital plate, palp and leg (2–6) segments for H. bruneiensis sp. nov. MALE FEMALE holotype paratype paratype Description. Male (holotype, in parentheses measurement of paratype, n = 1): Idiosoma L/W 960/780 (869– 1038/750–881, n = 3); L Cx-I+II 219 (208), Cx-III+IV 255 (256), total number of coxal setae 21 (19–21) on Cx-I, 20 (19–20) on Cx-II, 14 (12–14) on Cx-III, 13–15 (19) on Cx-IV. Further details of genital plate morphology ( Fig. 2B ) are given in Table 1. Capitulum ( Fig. 2E ) vL 193 (181); chelicera ( Fig. 2D ) total L 252 (234), claw L 51 (46), basal segment L 203 (197). Palp: for chaetotaxy see Fig. 2G (measurements in Table 1). Number of swimming setae on legs are presented in Table 2.

H. bruneiensis

male holotype female (paratypes, n =3) n =2 II-Leg-5 posterior 5 (5) 4–5 III-Leg-4 posterior 8–9 (7) 8 III-Leg-5 posterior 6–7 (7) 7 IV-Leg-4 anterior 8 (7–10) 7–8 IV-Leg-4 posterior 10 (8–10) 8 IV-Leg-5 anterior 0 0 IV-Leg-5 posterior 7 (6–7) 6 Female: Idiosoma L/W 959–1288/897–1144 (n = 2); L Cx-I+II 225, Cx-III+IV 268; number of coxal setae 24– 26 on Cx-I, 19–21 on Cx-II, 14–16 on Cx-III,14–15 on Cx-IV. Further details of genital plate morphology ( Fig. 2C ) are given in Table 1; egg maximum diameter L 147–184 (n = 3). Capitulum vL 181; chelicera total L 255, claw L 49, basal segment L 207. Palp: as in male, for chaetotaxy see Fig. 3A (measurements in Table 1). Number of swimming setae on legs are presented in Table 2.

Remarks. Due to the presence of more than two swimming setae on II-Leg-5 and absence of swimming setae on the anterior side of IV-Leg-5, Hydrodroma bruneiensis sp. nov. is most similar to H. kakadu Pešiċ & Smit, 2007 , a species known from Australia (Northern Territory) and New Caledonia. Hydrodroma kakadu can be distinguished by a lower number of acetabula (28–38 in male, 46–47 in female in generally 3–4 rows). Furthermore, Hydrodroma kakadu possesses much narrower palpal segments (L/H P-4, 4.8–5.0, P-5, 5.2–6.2 in both sexes, measurements taken from the paratypes, compare Fig. 3A with Fig. 3B ). Apart from the diagnostic morphological features, there are ecological differences between these two species: H. bruneiensis was taken from standing waters, while H. kakadu is rheophilous ( Pešiċ & Smit 2007).

Males of H. americanus Marshall, 1926 (in parentheses data taken from Wiles 1986) a species similar in the absence of swimming setae on the anterior side of IV-Leg-5, differ from H. bruneiensis sp. nov., in having twice as many setae on the genital plate as females (mean number of genital plate seta: 94± 14 in males, 41± 6 in females).

Wiles (1997) left his Hydrodroma specimens from Brunei unidentified. He mentioned that Hydrodroma specimens were regularly found in the tributaries of Temburong River in northern Brunei Darussalam.

Etymology. The species is named after the country where it was collected.

Habitat. Standing waters.

Distribution. Brunei Darussalam; known only from the type locality.

Figures

FIGURE 2 A – G. A. Hydrodroma bruneiensis sp. nov. (A – B, D – G = male, B = female): A = coxal and genital field; B – C = genital field; D = chelicera; E = capitulum; F = ejaculatory complex; G = palp, medial view. Scale bars = 100 μm.

FIGURE 3 A – B. A. Hydrodroma bruneiensis sp. nov., female. B. Hydrodroma kakadu Pešić & Smit, 2007, paratype female. A – B = palp, medial view. Scale bar = 100 μm.